Game ball incorporating a polymer foam

ABSTRACT

A game ball is disclosed that includes a polymer foam layer processed with an inert fluid blowing agent, such as nitrogen. The polymer foam may be a polyolefin material, such as polyethylene, polypropylene, and ethylvinylacetate, and the inert fluid blowing agent may have a relatively high-purity. The polymer foam may be manufactured with a process that includes impregnating a polymer with the inert fluid blowing agent and expanding the polymer by heating the polymer above a softening temperature of the polymer, reducing a fluid pressure surrounding the polymer, and cooling the polymer. The game ball may be a soccerball, football, or volleyball, for example, that includes the polymer foam.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional U.S. Patent Application is a divisional applicationof and claims priority to U.S. patent application Ser. No. 10/421,570,now U.S. Pat. No. 7,699,726 which was filed in the U.S. Patent andTrademark Office on Apr. 23, 2003 and entitled Game Ball Incorporating APolymer Foam, such prior U.S. patent application being entirelyincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to materials utilized in the constructionof a game ball. The invention concerns, more particularly, a game ballthat incorporates a polymer foam processed with an inert fluid blowingagent, such as nitrogen.

2. Description of Background Art

The game of soccer is played on a turf field having a length ofapproximately 100 meters and goals located at opposite ends of thefield. Competing teams attempt to advance a soccerball, which is alsoreferred to as a football, along the length of the field in oppositedirections without using their hands to grasp or otherwise affectmovement of the soccerball. The object of the game of soccer is for theplayers of one team to cooperatively advance the soccerball and placethe soccerball into their designated goal, thereby scoring a point.Simultaneously, the other team attempts to cooperatively thwart theadvance so as to regain possession of the soccerball and advance thesoccerball toward the opposite goal.

The Fédération Internationale de Football Association (FIFA) promulgatesstandards that rank soccerballs as being either approved or inspected.Soccerballs bearing the approved denomination are generally recognizedas embracing the quality necessary for international competition,whereas soccerballs bearing the inspected denomination may be utilizedfor lower competition levels or practice. In order to qualify for theapproved denomination, a soccerball must fall within a narrow range oftolerances based upon such properties as weight, circumference,sphericity, pressure loss, water absorption, rebound, and shape and sizeretention.

The standards set by FIFA generally relate to the physical propertiesand performance of the soccerball rather than the specific structure ofthe soccerball or the materials utilized in the various components ofthe soccerball. Accordingly, soccerball manufacturers often vary thestructure and materials of commercially-available soccerballs in anattempt to enhance the physical properties of the soccerball. Ingeneral, however, modern soccerballs have a substantially conventionalconfiguration, as discussed below.

A conventional soccerball is substantially spherical and has a layeredconstruction that includes a cover, a supportive structural lining, andan inflatable bladder. The cover is generally formed from a plurality ofdurable, wear-resistant panels that are stitched together along abuttingsides to form a closed surface. The traditional soccer ball cover ismodeled on a regular, truncated icosahedron and includes, therefore,twenty hexagonal panels and twelve pentagonal panels, and a plurality ofother panel configurations are also conventionally utilized. Althoughthe cover may be formed from full-grain leather, the cover ofconventional soccerballs is often formed from polyurethane or polyvinylchloride materials. The lining is generally located between the coverand the bladder to resist the outward pressure provided by the bladder,thereby retaining a spherical and dimensionally-consistent shape.Depending upon the manufacturer, the lining may be formed of naturalcotton textiles, polyester textiles, or textiles that incorporate bothcotton and polyester fibers. In addition to textiles, the lining mayalso incorporate a latex layer, for example. The bladder, which is theinner-most layer of the conventional soccerball, is formed of a materialthat is substantially impermeable to air, such as natural rubber, butylrubber, and polyurethane. The bladder generally includes a valvedopening, accessible through the cover, to facilitate the introduction ofair. When inflated, the bladder expands and places a uniform outwardpressure on the lining and cover, thereby inducing the soccerball totake a substantially spherical shape.

In addition to the cover, lining, and bladder, a soccerball may alsoincorporate a polymer foam layer to enhance pliability and cushioning.The foam layer generally has a thickness of 1 to 2 millimeters and ispositioned between the cover and lining. Suitable materials for the foamlayer include most polyolefin foams, which are prepared by thepolymerization of olefins as the sole monomers. Examples of polyolefinfoams include polyethylene, polypropylene, and ethylvinylacetate.

A first manufacturing process commonly employed to produce polyolefinfoam suitable for the conventional soccerball utilizeschlorofluorocarbons, hydrofluorocarbons, or volatile hydrocarbons as ablowing agent. The resulting polyolefin foam is not cross-linked and mayrelease chemicals that are considered to be detrimental to the globalenvironment. A similar release of chemicals may also result from errorsin the manufacturing process itself.

A second manufacturing process commonly employed to produce polyolefinfoam suitable for the conventional soccerball utilizes a chemicalblowing agent that expands through a decomposition reaction. Inmanufacturing the foam, a chemical such as azodicarbonamide isincorporated into polyolefin resin. A decomposition reaction involvingthe azodicarbonamide is then initiated by heat and produces gasses, suchas nitrogen, carbon monoxide, carbon dioxide, and ammonia. The variousgasses expand the polyolefin resin, thereby producing the polyolefinfoam. A significant portion of the azodicarbonamide remains as residue,however, within the resulting polyolefin foam. Depending upon thedensity of the polyolefin foam, approximately 10% of the foam weight maybe due to the azodicarbonamide residue. Accordingly, only 90% of thepolyolefin foam weight is available to contribute to the mechanicalperformance of the polyolefin foam. Furthermore, if a soccerballincorporating a polyolefin foam is exposed to high ambient temperatures,then the azodicarbonamide decomposition reaction may reinitiate, therebyaltering the properties of the polyolefin foam within the soccerball.

SUMMARY OF THE INVENTION

The present invention is a game ball that includes a polymer foamprocessed with a nitrogen blowing agent. As discussed above in theBackground of the Invention, a conventional foam is often incorporatedinto game balls, such as a soccerball. The conventional foam may beprocessed with chlorofluorocarbon, hydrofluorocarbon, or volatilehydrocarbons as a blowing agent, which is detrimental to theenvironment. Alternately, the conventional foam may be formed with achemical blowing agent, such as azodicarbonamide, that leaves a residuewithin the resulting foam. In contrast with the conventional foam, thepolymer foam utilized in the game ball of the present invention isformed with a nitrogen blowing agent that does not detrimentally affectthe environment or leave a substantial chemical residue. Alternately, avariety of other generally inert fluids may be utilized as the blowingagent, including helium, neon, or argon, for example.

In forming the polymer foam, the nitrogen blowing agent is utilized toimpregnate a polymer material, which may be a polyolefin such aspolyethylene, ethylvinylacetate, or polypropylene. Thenitrogen-impregnated polymer material is then heated and the pressurearound the polymer material is reduced, thereby causing the nitrogen toexpand. Upon cooling, the expanded polymer material solidifies and formsthe resulting polymer foam. Nitrogen of varying purities is suitable asthe blowing agent. Nitrogen with at least 99.9% purity, however, isgenerally utilized in the manufacture of nitrogen-blown polymer foams.

The nitrogen-blown polymer foam may be incorporated into a variety ofgame ball types, including soccerballs, volleyballs, or footballs, forexample. Such game balls generally include a cover that is formed of aplurality of panels connected along abutting edges. The nitrogen-blownpolymer foam is positioned within the cover, and other layers thatinclude a textile layer and a bladder may be located within the polymerfoam.

The advantages and features of novelty characterizing the presentinvention are pointed out with particularity in the appended claims. Togain an improved understanding of the advantages and features ofnovelty, however, reference may be made to the following descriptivematter and accompanying drawings that describe and illustrate variousembodiments and concepts related to the invention.

DESCRIPTION OF THE DRAWINGS

The foregoing Summary of the Invention, as well as the followingDetailed Description of the Invention, will be better understood whenread in conjunction with the accompanying drawings.

FIG. 1 is a perspective view of a soccerball in accordance with thepresent invention.

FIG. 2 is a perspective view of the soccerball with selected layerspeeled away.

FIG. 3 is a table presenting data from an experimental analysis ofvarious conventional and prototype soccerballs.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion and accompanying figures disclose a game ballin accordance with the present invention. The game ball is discussed anddepicted as a soccerball incorporating a polymer foam processed with anitrogen blowing agent. Alternately, a variety of other generally inertfluids may be utilized as the blowing agent, including helium, neon, orargon, for example. The following discussion is specifically directed tothe soccerball in order to demonstrate the structure and features of anexemplar game ball that incorporates the polymer foam. Those of ordinaryskill in the relevant art will appreciate, however, that the principlesdisclosed herein are equally applicable to other types of game balls,including volleyballs and footballs, for example.

A game ball 10 having the configuration of a soccerball is depicted inFIGS. 1 and 2. The primary elements of ball 10 are cover 20, a foamlayer 30, a latex layer 40, a textile layer 50, and a bladder 60. Cover20 is formed from twenty hexagonal panels 21 and twelve pentagonalpanels 22 that are stitched together along abutting sides to form anexterior surface for ball 10. The various panels 21 and 22 are depictedas having the shapes of equilateral hexagons and pentagons. In furtherembodiments, panels 21 and 22 may have non-equilateral shapes; selectedpanels 21 and 22 may be formed integral with adjacent panels 21 and 22to form bridged panels that reduce the number of seams requiringstitching; or panels 21 and 22 may have other shapes that combine in atessellation-type manner to form cover 20. The material selected forcover 20 may be leather, polyurethane, polyvinyl chloride materials, orother materials that are both durable and wear-resistant.

Foam layer 30 is located adjacent to an interior surface of cover 20 andenhances the overall pliability and cushioning of ball 10. The thicknessof foam layer 30 may range from 0.5 millimeters to 4.5 millimeters.Suitable materials for foam layer 30 include a variety of polymer foams,such as polyolefin foams, that are processed with a nitrogen blowingagent. Examples of polyolefin foams include, for example, low-densitypolyethylene, high-density polyethylene, polypropylene, andethylvinylacetate. Alternately, a variety of other generally inertfluids may be utilized as the blowing agent for the polymer foam,including helium, neon, or argon, for example.

As discussed in the above Background of the Invention, a polyolefin foamis often incorporated into the conventional soccerball. The polyolefinfoam may be processed with chlorofluorocarbon, hydrofluorocarbon, orvolatile hydrocarbons as a blowing agent, which is detrimental to theenvironment. Alternately, the polyolefin foam may be formed with achemical blowing agent, such as azodicarbonamide, that leaves a residuewithin the resulting polyolefin foam. The residue contributes to theweight of the polyolefin foam, and the conventional soccerball, but doesnot contribute to the mechanical performance of the polyolefin foam.Furthermore, the azodicarbonamide may continue to decompose after thepolyolefin foam is incorporated into the conventional soccerball.Further decomposition may increase the cell size within the polyolefinfoam, thereby changing the properties of the foam.

To address the issues with conventional polyolefin foam materials, foamlayer 30 of the present invention incorporates a polymer foam processedwith a nitrogen blowing agent. Such foams, which are referred tohereafter as nitrogen-blown polymer foams, are commercially-availablefrom Zotefoams Inc. of Croyden, England. under the tradenames ofPLASTAZOTE, which is a closed cell, cross-linked polyethylene foam;EVAZOTE and SUPAZOTE, which are closed cell, cross-linked ethylenecopolymer foams; and PROPOZOTE, which is a closed cell polypropylenecopolymer foam. In contrast with the chlorofluorocarbon,hydrofluorocarbon, or volatile hydrocarbon blowing agents that arecommonly utilized is conventional polymer foam production, nitrogen isnaturally-abundant in the atmosphere and considered to the generallyinert, thereby promoting global environmental well-being and the healthof the individuals producing and handling the nitrogen-blown polymerfoams. In addition, nitrogen-blown polymer foams do not include achemical residue, as with polymer foams that are blown with thedecomposition reaction of azodicarbonamide. In comparison withconventional polymer foams, therefore, the lack of chemical residue inthe nitrogen-blown polymer foams increases the mechanical performanceper unit weight.

A further advantage to nitrogen-blown polymer foams relates to theresulting cells, or gas-filled pockets, within the foam. Theconventional polymer foams include cells with a wide range of sizes. Incontrast, the cell sizes of nitrogen-blown polymer foams aresubstantially more uniform, thereby imparting more consistent propertiesthroughout the foam. This is not to imply that nitrogen-blown polymerfoams are free from varying cell sizes. Rather, the frequency with whichvarying cell sizes occur in nitrogen-blown polymer foams issignificantly lower than with conventional polymer foams. Accordingly,the standard deviation in cell size of nitrogen-blown polymer foams isless than the standard deviation in cell size of the conventional foammaterials.

Nitrogen-blown polymer foams are generally manufactured through athree-step process that includes extrusion, impregnation, and expansion.In the extrusion step, a base resin and additive ingredients are mixedand fed into an extruder, with the additive ingredients includingcoloring agents, fire retardants, or plasticizers, for example. The baseresin and additive ingredients are then extruded in a desired shape toform a cross-linked plastic. Cross-linking may be achieved throughirradiation or a chemical, for example In the impregnation step, theextruded plastic is placed in a high-pressure autoclave and heated to atemperature that exceeds the softening temperature. The plastic is alsosubjected to relatively high pressures of substantially pure nitrogensuch that the nitrogen dissolves into the heated plastic material. Theplastic is subsequently cooled, thereby confining or locking thenitrogen within the plastic. In the expansion step, thenitrogen-impregnated plastic is positioned in a low-pressure autoclaveand again heated to a temperature that exceeds the softeningtemperature. A moderate air pressure that surrounds the plastic duringthe heating is then reduced such that the nitrogen within the plasticexpands, thereby foaming the plastic in a uniform manner. Accordingly,only nitrogen is utilized as the blowing agent, rather thanchlorofluorocarbon, hydrofluorocarbon, volatile hydrocarbons, orazodicarbonamide, which may have an adverse effect upon the environmentor the polymer foam itself.

Nitrogen of varying purities is suitable as the blowing agent in theprocess discussed above. High-purity nitrogen, however, is generallyutilized in the manufacture of nitrogen-blown polymer foams. Forpurposes of the present application, nitrogen having a purity of 99.9%may be considered as having high-purity. A benefit to utilizinghigh-purity nitrogen gas relates to the predictable expansion propertiesof the high-purity nitrogen at various pressure-temperaturecombinations. Predictability of the expansion would decrease with theintroduction of additional gasses due to the different expansionproperties of the additional gasses at the various pressure-temperaturecombinations. Accordingly, the use of high-purity nitrogen providespredictable expansion in the polymer and results in a uniform resultingfoam. If other inert fluid blowing agents are utilized, the other inertfluid blowing agents may exhibit a high-purity of 99.9%.

In manufacturing ball 10, cover 20, foam layer 30, latex layer 40, andtextile layer 50 are bonded together to form a single laminatedmaterial. Heat, pressure, and/or an adhesive may be utilized in bondingthe components. The individual panels 21 and 22 are die cut from thelaminated material and joined together. Bladder 60 is then placed withinthe joined elements, thereby substantially completing the manufacture ofball 10.

In addition to cover 20 and foam layer 30, ball 10 includes latex layer40, textile layer 50, and bladder layer 60. Latex layer 40 may beutilized within ball 10 and is located adjacent to foam layer 30 andopposite cover 20. The purpose of latex layer 40 is to provide energyreturn. Textile layer 50 is positioned between latex layer 40 andbladder 60 and may be formed of natural cotton textiles, polyestertextiles, or textiles that incorporate both cotton and polyester fibers.Bladder 60 is the inner-most layer of ball 10. The material formingbladder 60 is substantially impermeable to air, and may include naturalrubber, butyl rubber, or polyurethane. Bladder 60 may include a valvedopening (not depicted) that extends through textile layer 50, latexlayer 40, foam layer 30, and cover 20 to facilitate the introduction ofair. Alternately, the valved opening may be slightly recessed below thelevel of cover 20. When inflated the proper pressure, bladder 60expands, thereby inducing ball 10 to take a substantially sphericalshape.

An experimental analysis compared the physical properties andperformance of conventional soccerballs with a plurality of prototypesoccerballs having the configuration of ball 10. As a control measure inthe experimental analysis, the overall structure of the conventionalsoccerballs and the prototype soccerballs were substantially identical,with the exception of the polymer foam utilized for the foam layer.Whereas the conventional soccerballs incorporated a conventionalpolyethylene foam having a thickness of 2 millimeters, the prototypesoccerballs utilized nitrogen-blown polymer foams with a thickness of 2millimeters. Differences between the conventional soccerballs and theprototype soccerballs may be generally attributed, therefore, to thedifferent types of foam.

Three types of prototype soccerballs were prepared for the experimentalanalysis, and will be distinguished hereafter as Prototype SoccerballsA, B, and C. Prototype Soccerballs A incorporated a nitrogen-blownpolyethylene foam, whereas Prototype Soccerballs B and C utilized twodifferent types of nitrogen-blown ethylene copolymer foams. The FIFAstandards relating to the approved denomination require that soccerballshave, inter alia, a weight between 420 and 445 grams and a circumferencebetween 68.5 and 69.5 grams. All soccerballs, whether conventional orprototype, exhibited a weight and circumference within the FIFA weightand circumference ranges for the approved denomination.

The conventional and prototype soccerballs were subjected to rebound,size expansion, sphericity deviation, air pressure loss, and waterabsorption tests, which are also included in the FIFA standards. Inaddition, the soccerballs were tested for abrasion losses. The resultsof the experimental analysis is presented in the table of FIG. 3. Ingeneral, Prototype Soccerballs A, B, and C performed better than theconventional soccerballs, with all soccerballs falling within the FIFAstandards for the approved designation on all tests. The rebound testinvolved dropping the various soccerballs from a height of 2 meters ontoa steel plate and measuring the rebound height. Each of PrototypeSoccerballs A, B, and C exceeded the rebound height of the conventionalsoccerballs. The size expansion, sphericity deviation, air pressureloss, and abrasion loss tests were conducted by propelling the varioussoccerballs at approximately 50 kilometers per hour toward a steel platefor 2000 cycles. Prototype Soccerballs A, B, and C each exhibited lesscircumferential expansion, less pressure loss, and less abrasion thanthe conventional soccerballs, and Prototype Soccerballs B exhibited lesssphericity deviation than the conventional soccerballs. The waterabsorption test was conducted by immersing the various soccerballs inwater for a predetermined period of time and measuring the resultingmass change, with Prototype Soccerballs A and C both exhibiting lessoverall absorption. The experimental analysis of the soccerballsdemonstrated, therefore, that soccerballs having the configuration ofball 10, which incorporates a nitrogen-blown polymer foam, generallyperforms in a manner that exceeds the conventional soccerball.

The generally enhanced performance of Prototype Soccerballs A, B, and C,when compared to the conventional soccerballs, may be attributed to avariety of factors relating to the nitrogen-blown polymer foams. Asdiscussed above, conventional foam materials may have a less uniformcell structure and may incorporate a chemical residue that contributesto the weight of the foam, but does not contribute to the mechanicalperformance of the foam. The cell structure and residue weight ofconventional foam materials, either individually or in combination, mayaccount for the enhanced performance of Prototype Soccerballs A, B, andC.

The specific configuration of ball 10 described above may be alteredwithin the scope of the present invention. For example, latex layer 40or textile layer 50 may be omitted. Ball 10 is disclosed as asoccerball, and the specific configuration disclosed for cover 20 isgenerally specific to soccerballs. The present invention is intended tocover volleyballs and footballs, however, that incorporate anitrogen-blown polymer foam. In further embodiments, therefore, ball 10may be a volleyball or football, for example, which has a substantiallydifferent cover configuration, and, in the case of the football,substantially different shape. Accordingly, various modifications may bemade to the structure of ball 10 without departing from the scope of thepresent invention.

The present invention is disclosed above and in the accompanyingdrawings with reference to a variety of embodiments. The purpose servedby the disclosure, however, is to provide an example of the variousfeatures and concepts related to the invention, not to limit the scopeof the invention. One skilled in the relevant art will recognize thatnumerous variations and modifications may be made to the embodimentsdescribed above without departing from the scope of the presentinvention, as defined by the appended claims.

1. A method of manufacturing a game ball having a cover and a textilelayer, the method comprising steps of: obtaining a closed cell,cross-linked, foam material manufactured through a process thatincludes: impregnating a polyolefin selected from the group consistingof low-density polyethylene, high-density polyethylene, polypropylene,and ethylvinylacetate with a nitrogen blowing agent having at least99.9% purity, and expanding the polyolefin by heating the polyolefinabove a softening temperature of the polyolefin, reducing a fluidpressure surrounding the polyolefin, and cooling the polyolefin to formthe closed cell foam material; and incorporating the closed cell foammaterial into the game ball between the cover and textile layer, whereinthe foam layer has a thickness ranging from 0.5 to 4.5 mm; wherein themethod forms a game ball having a rebound ranging from 138 to 140 cm,and a size expansion of from 0.54 to 0.66 cm.
 2. The method of claim 1,further including a step of enclosing the foam material with the coverthat includes a plurality of panels connected together along abuttingedges of the panels.
 3. The method of claim 2, wherein the step ofenclosing the foam material includes manufacturing the panels to includetwenty hexagonal panels and twelve pentagonal panels.
 4. The method ofclaim 1, further including a step of placing the textile layer and abladder within the foam material.